#define _CRT_SECURE_NO_WARNINGS 1


#include<iostream>

using namespace std;

int main()
{
	double r1 = 0, r2 = 0;
	cin >> r1 >> r2;
	printf("%.2lf\n", 1.0 / (1.0 / r1 + 1.0 / r2));

	return 0;
}